Treatment by pressure of cast and forged steel tubes



A. E'. GUY. TREATMENT BY PRESSURE 0F CAST AND FORGED STEEL TUBES.

' APPLICATION FILED OCT. 17. 1918.

A1 9,845. ate tedJune 13, 1922.

/9 I Jnvc wtoz ALBERT E. GUY, OF THE UNITED STATES ARMY.

Cl.13Jil.Z-!J1NEIENT BY PRESSURE OF CAST AND FORGED STEEL TUBES.

Specification of Letters Patent. Patented J 13 1922 Application filed October 17, 1918. Serial No. 258,652.

(FILED UNDER THE ACT OF MARCH 3, 1883, 22 STAT. L, 625.)

T 0 all whom it may concern Be it known that I, .ALBERT E. GU-Y, inajor, Ordnance Dept, U. S. A., a citizen of the United States, stationed at Washington, D. C., have invented an Improvement in Treatment by Pressure of Cast and Forged Steel Tubes, of which thefollowing is a specification.

The invention described herein may be used by theGovernment, or any of its officers or employees in prosecution of work for the Government, or by any other person in the United States, without payment of any royalty thereon. v

This invention relates to the treatment by pressure of cast and forged steel tubes, whereby the structure of the inner walls of the tube is permanently changed to adapt itto withstand stresses which would otherwise strain it beyond the elastic strength of the steel.

The invention is intended particularly for guntubes, which must withstand very high internal pressure each time a shot is fired; but it is not restricted to gun tubes. It is also adapted for fitting linings: in cylinders, tubes and the like, and especially for .relining gun tubes.

The objects of theinvention are rapidity and ease of operation, low cost, and adaptability to different conditions of manufacture and use. A further object is the pro duction of walls of varying strength, conforming to the pressures to bewithstood atsuccessive points along the tube.

The preferred mode of carrying out the invention as applied to a gun tube is hereinafter described, and what is claimed as the invention appears from the appended claims.

Reference is made to the accompanying drawings, wherein 4 v Fig. 1 is a longitudinal sectional view of a gun forging ready for treatment by pressure;

Fig. 2 is a cross-sectional view of the same on the line 22 of Fig. 1, looking in the direction of the arrows;

Fig. 3 is a view similar to Fig. 1 after the pressure treatment showing, greatly exaggerated the effect of the treatment, the origp nal bore being shown in dotted lines;

Fig. 4: is a similarview of the gun tube after boring out ready for the rifling and finishing operations;

Fig. 5 is av view similar to Fig. 1, showing a relined gun ready for treatment by pressure;

Fig. 6 is a view similar to Fig. 1, showing a modification of the process.

Figure 7 is a view similar to Figure 1,

showing slightly modified means for carrying out the method, in which a core is used internally of the gun tube.

Referring to Fig. l, the gun forging 11 s rough turned or forged to approximately 1ts final dimensions on the exterior, the interior being left at the breech end slightly smaller than the finished size. The bore is made tapering or reduced by steps from the breech to the muzzle for a purpose which will hereinafter appear.

The ends of thebore are closed by any suitable means, such as the plug 12 which is screwed into the breech end and the plug 13 'which is screwed into the muzzle end. The

plug 12 has a passage 14 leading through it, through which a filler 15 of molten lead or other suitable fluid may be conducted to fill the interior of'the gun, as shown in Fig. 3, after which the passage is closed by a suitable stopper 16. Any fluid having a coefficient of expansion suliicientiy different from that of steel may be used.

The passage 1 1 in the plug 12 is a convenience, but is not necessary since the filler may be placed in tl'ie tube prior to the insertion of the plug.

The gun and contents are heated (or cooled if the contents has a lower coefficient of expansion than steel) until the more rapidly expanding lead stretches the inner wall of the gun beyond the elastic limit of the steel and a permanent deformation or set of the inner layers of steel results. The operation is stopped before the outer layers of steel are stretched beyond the elastic limit of the steel. Upon cooling of the gun and contents, the outer layers of the steel tend to return to their original size, thereby compressing the inner layers, which have been stretched too far to returnto their original size and remain slightly stretched and hence under compression from the outer layers.

The effect of the tapered or stepped down bore is to vary the stretching of the inner walls caused by the pressure within the bore, in other words, to vary the compression of the inner part of the wall at successive points along the bore to suit the powder pressure and the designed thickness of the wall, both of which vary along said successive points, and each according to well recognized laws.

The resulting condition of the metal in the inner and outer regions of the gun tube is analogous to that in theinner and outer tubes or bands of a composite gun formed by shrinking on the outer band to compress the metal in the inner tube.

The next step in the process is to remove the plugs 12 and 13 and the lead or other filler, and bore out the gun to size, as shown in Fig. l, whereupon it is ready for rifling, fitting the breech and finishing.

This process is particularly applicable to the retubing or relining of worn out guns. After firing a certain number of rounds a gun loses its accuracy and range due to the fact that the bore and. rifling have, become so worn and eroded that the powder gases are no longer properly occluded by the. copper bands on the projectile and that the latter is not properly guided in its course along the bore. The gun must then be taken out of service and sent to the repair base where usually it is machined out to receive an inner tube or liner which may be bored and rifled to the size of the original gun or to another bore as determined by circumstances. Various methods have been devised for inserting and securing the liner, in the gun but so far no method has been found satisfactory enough to be accepted as standard. This desideratumcan be attained by the application of my process.

Fig. 5 shows the application of this process to securing permanently the lining in a gun tube. The gun 1.1 tr; be relined is first machined out to receive the inner tube or lining 16, which is inserted and its ends are closed by any suitable means, such as by the breech plug 17' and the muzzle plug 18, which are screwed into the lining as shown. A closable aperture 19 isprovided in the breech plug 17. through which the fluid filler mayfbe introduced.

By filling the liner with a suitable substance such as lead-for instance, and subjecting the'ensemble to appropriate heat, the =liner is'expanded, and upon cooling of the 60 gun the liner is securely held in place under the desired conditions of shrinkage and of 1 compresslon of the inner layers of both the gun and the liner.

-Various modified forms of applying the invention to bring about modified results may be resorted to, such as for instance by so arranging the elements as to localize the distension and thereby control the amount of set at different points along the tube, as shown in Fig. 6, which illustrates the application of this process to a gun bore having a stepped down inner surface as shown at 20, providing shoulders'21 against which a divisional plate 22 may rest.

The tube diameter and volume of the filler maybe increased or decreased at any desired point in the tube to bring about a suitable distension, or fillers of different coeflicicnts of expansion may be employed at different points in the tube with or without dividing elements, and in this manner the desired degrees of strain or set -are provided for where required. The volume of the filler may be varied to suit the degree of distension desired by introducing a core of suitable material into the tube. The core may be of the same material as the tube, or it may of any material having a different coefficient of expansion from the filler.

In Figure 7 I have shown such a core 13 preferably carried by the end closure-plug 13 and extending axially of thetube 11 The other end plug 12 is apertured at H for the insertion in the tube of the molten filler.

From the foregoing description it is evident that a relatively great saving in time, labor, and materials can be had by using my invention for strengthening a gun tube, as compared with processes which require the shrinking on of jackets around the outside of the tube, or the separate treatment of successive lengths of the tube.

I claim the following as my invention: I

l. Themethod of treating a metallic tube which consists in filling the tube witha substance having a coefficient of expansion under heat greater than that of the tube closing the ends of the tube, and heating the tube to expand said substance and tube until the greater expansion of said substance permgnently distendsthe inner layers of the tu e.

2. The method of treating a metallic tube which consists in filling the tube witha medium having a coefiicient of expansion diftube and subjecting the mass to achange of temperature.

'ferent from that of the tube, sealing the a medium having a coefficient of expansion different from that of the tube, sealing the tube and changing the temperature of the mass.

5. The method of distending the inner wall of a tube which consists in tapering the inner wall of said tube, filling the tube with a medium having a coeiiicient of expansion different from that of the tube, sealing the tube and changing the temperature of the mass.

6. lhe method of treating a metallic tube which consists in temporarily sealing one end thereof, then filling said tube with a medium having a coefficient of expansion under heat greater than that of the tube, n. temporarily sealing the other end of s. tube, and finally heating said tube to expand said filler and tube until the greater expansion of said filler permanently distends the inner layers of said tube.

7. The method of forming a metallic tube which consists in finishing the exterior thereof to substantially the desired size, rough boring the tube with a taperingbore, filling the tube with a medium having a coefficient of expansion different from that of the tube, applying pressure within the tube by changing the temperature of said medium until the inner wall of the tube has taken a permanent set and finishing the bore of the tube to size.

8. The method of forming a metallic tube which consists in finishing the exterior thereof to substantially the desired size, rough boring the tube, filling the tube with a medium having a coefficient of expansion different from that of the tube, applying pressure within the tube by changing the temperature of said medium until the inner wall of the tube has taken a permanent set and finishing the bore of the tube to size.

9. The method of treating a metallic tube which consists in inserting therein a core, filling the space between the core and the tube with a medium having a coefficient of expansion different from that of the tube, and changing the temperature of said medium to effect the permanent distension of the inner layers of the tube.

10. The method of treating a metallic tube which consists in inserting therein a core having a coefficient of expansion different from that of the tube, filling the space be tween said core and the tube with a medium having a coeiiicient of expansion different from that of the tube, and changing the temperature of said medium and said core.

11. The method of treating a metallic tube which consists in filling the same at intervals with different mediums having different coefficients of expansion and all of said mediums having coefficients of expansion different from that of the tube, and in changing the temperature in said mediums to effect different degrees of distension of the inner layers of the tube in different areas thereof.

12. The method of relining gun tubes which consists in inserting a liner in a tube, filling the said liner with a medium having a coefficient of expansion different from that of the liner and the tube and subjecting the mass to a change of temperature until the inner wall of the liner has taken a permanent set.

ALBERT E. GUY. 

